1. Field of the Invention
The present invention relates to an imaging system capable of improving the quality of image data obtained by imaging an optical image of a subject using restoration processing, an imaging apparatus including the imaging system, a portable terminal apparatus including the imaging system, an onboard apparatus including the imaging system, and a medical apparatus including the imaging system.
2. Description of Related Art
An imaging system that forms an optical image of a subject, which is focused on a light receiving surface through an imaging lens, by using an imaging device, such as a CCD device or a CMOS device, having the light receiving surface on which a plurality of light receiving pixels are two-dimensionally arrayed is known.
In addition, an onboard camera or a portable cellular phone camera in which an imaging system having an imaging lens designed such that the depth of field increases is attached directly on a circuit board is known as an example of such an imaging system (refer to JP-A-2007-147951). Such an imaging system directly attached to a circuit board is designed to have a small device size since the size is limited.
In addition, an onboard camera or a portable cellular phone camera with high performance in which an imaging system, in which the number of light receiving pixels of an imaging device is increased and the resolving power of an imaging lens is improved, is mounted is also known. Among such onboard cameras or portable cellular phone cameras with high performance capable of obtaining high-resolution images, one in which the resolving power of an imaging lens is close to a diffraction limitation is also known.
On the other hand, it has been requested to further improve the resolution for an image obtained by using such an imaging system.
In order to improve the resolution of an image obtained by an imaging system, it is necessary to increase the number of light receiving pixels and to increase the resolving power of an imaging lens. That is, for example, by increasing the pixel density of light receiving pixels arrayed on a light receiving surface of an imaging device and increasing the resolving power of an imaging lens such that a point image projected onto the light receiving surface through the imaging lens falls within a range of one light receiving pixel, the resolution of the image obtained by using the imaging system can be improved.
Here, increasing the pixel density of light receiving pixels that form the imaging device without making the device size large may be realized relatively easily by an improvement in a technique in recent years.
On the other hand, it is very difficult to improve the resolving power of an imaging lens. That is, in order to improve the resolution of the imaging lens without making the size of the imaging lens large or making a depth of field small, it is necessary to suppress a shape error, an assembly error, and the like of each lens that forms the imaging lens. However, since there is an imaging lens the resolving power of which is already increased up to a level close to the diffraction limitation, there is a problem that it is very difficult to increase the resolving power by further improving manufacturing accuracy (for example, machining accuracy, assembly accuracy, and adjustment accuracy).
However, in manufacturing an imaging system having such an imaging lens capable of forming an image with high resolution, it is difficult to increase the yield due to difficulties in manufacture. That is, since image data allowing an image having an intended resolution to be formed cannot be generated, there is a possibility that many imaging systems will be out of a production line for readjustment or reassembly. In addition, an imaging system removed from the production line is reproduced such that image data capable of forming an image with the intended resolution can be generated by specifying the cause and performing modification.
However, there are various causes of reducing the resolution of an image expressed by image data output from an imaging system. For example, various causes, such as shape errors (surface shape error, thickness error, and eccentric error of a lens) of an individual lens used to form an imaging lens, assembly and adjustment errors of an imaging lens (shift error and tilt error of a lens and air space error between lenses), and a positional error of an imaging device with respect to an imaging lens, may be considered. For this reason, there is a problem that a cost is significantly increased for reproduction of an imaging system capable of generating high-quality image data, which allows an image with the intended resolution to be formed, by specifying a cause of the reduction in resolution and performing readjustment and reassembly.